Stadium: Centre Court Round: 62 Ground: Clay
| ITF Germany F10 | 2018/08/01 14:05 | Mertens, Nico v Facundo Mena | 2-6,2-6 |
| ITF Germany F10 Qual | 2018/07/30 12:00 | Mertens, Nico v Nery Junior, Osni | 4-6,5-7 |
| ITF Germany F10 Qual | 2018/07/29 15:30 | Mertens, Nico v Koch, Niklas | 6-4,7-6 |
| ITF Germany F9 | 2018/07/24 10:00 | Mertens, Nico v Manuel Guinard | 0-6,6-4,4-6 |
| ITF Bosnia and Herzegovina F3 | 2018/05/29 10:40 | Mertens, Nico v Nerman Fatic | 4-6,3-6 |
| ITF Czech Republic F2 Qual | 2018/05/21 08:00 | Mertens, Nico v Franek, Michal | 3-6,2-6 |
| ITF Czech Republic F2 Qual | 2018/05/20 08:00 | Mertens, Nico v Cyprich, Radek | 6-2,6-2 |
| ITF Tunisia F11 | 2018/03/19 08:30 | Mertens, Nico v Munoz-Abreu, Jordi | 1-6,3-6 |
| ITF Belgium F7 Qual | 2018/08/04 07:30 | Leiva Biason, Oscar Mattias v Velasquez Meza, Javier Alonso | 6-0,6-0 |
| ITF Belgium F6 Qual | 2018/07/28 09:30 | Delmas, Amaury v Leiva Biason, Oscar Mattias | 6-0,6-3 |
| ITF Germany F9 | 2018/07/22 08:00 | Leiva Biason, Oscar Mattias v Dettinger, Moritz | 2-6,1-6 |
| ITF Belgium F4 | 2018/07/14 07:00 | Naser, Javier v Leiva Biason, Oscar Mattias | 6-2,6-0 |
| ITF Germany F7 | 2018/07/09 08:00 | Andres Urrea v Leiva Biason, Oscar Mattias | 7-6,6-2 |
| ITF Belgium F2 Qual | 2018/06/24 14:50 | Leiva Biason, Oscar Mattias v Paul Valsecchi | 2-6,1-6 |
| ITF Belgium F2 Qual | 2018/06/23 13:20 | Leiva Biason, Oscar Mattias v Zekri, Yannis | 6-1,6-0 |
| ITF Egypt F13 | 2018/04/08 08:00 | Taweel, Issam Haitham v Leiva Biason, Oscar Mattias | 6-2,6-0 |